1. Field of the Invention
The present invention relates to a pump module that regulates the fluid pressure of a hydraulic system.
2. Description of Related Art
Some internal combustion engines contain fuel injectors that inject a highly pressurized spray of fuel into the combustion chamber. Fuel injectors are frequently used in combustion ignition engines which run on diesel fuel. Fuel injectors typically contain a spring return hydraulically driven intensifier that increases the pressure of the fuel. The energy that drives the intensifier is provided by a working fluid that is pressurized by an external pump. The flow of working fluid into the fuel injector is controlled by a solenoid control valve that is switched between open and closed positions by an electronic controller. In an engine with multiple fuel injectors, the continuous opening and closing of the control valves may cause variations in the pressure of the working fluid.
FIG. 1 shows a prior art fuel system for an internal combustion engine. Each fuel injector 2 has an accumulator 4 that compensates for instantaneous changes in oil pressure. The accumulator 4 is coupled to a pump 6. The pump 6 and injector 2 are connected to an oil pan 8 to complete the loop. Coupled to the output of the pump 6 is an electronic relief valve 9. The relief valve 9 contains an electronically controlled throttle valve which can vary the pressure drop across the valve. The electronic relief valve is connected to a central engine microcontroller.
To decrease the oil pressure of the system, the microcontroller provides a signal to close the throttle valve and increase the pressure drop across the relief valve. Likewise to increase the pressure within the system, the throttle valve is opened to decrease the pressure drop across the relief valve. In the prior art system the pump still provides the same amount of work even when the system oil pressure is varied by the relief valve. Pump work tends to reduce the energy efficiency of the engine and the life of the pump. It would therefore be desirable to have a fluid pressure control system for an internal combustion engine that reduces the work requirement of the pump when energy from the pump is not required.